Clean up remaining core aliased methods

And also one for zlib.

Previously I just checked core/*/shared.
But some didn't use that, and others I skipped by accident.

I used the following script (with `--disable-gems`) to find aliased methods:

```rb
require "objspace"

r = {}
ObjectSpace.each_object(Module) do |mod|
  next if mod.inspect.include?("<Object:")
  methods = mod.public_instance_methods.map { mod.instance_method(it) }
  methods += mod.public_methods.map { mod.method(it) }
  methods.each do |meth|
    to_find = methods.select { it.name != meth.name }
    next if to_find.none? { it == meth }
    next if meth.owner != (meth.is_a?(Method) ? mod.singleton_class : mod )
    r[mod] ||= []
    r[mod] << meth
  end
end

r = r.transform_values do |methods|
  methods.group_by(&:itself).values
end

pp r
```

Author: Earlopain

core/basicobject/equal_spec.rb

@@ -1,54 +1,7 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/kernel/equal'
 
 describe "BasicObject#equal?" do
-  it "is a public instance method" do
-    BasicObject.public_instance_methods(false).should.include?(:equal?)
-  end
-
-  it_behaves_like :object_equal, :equal?
-
-  it "is unaffected by overriding __id__" do
-    o1 = mock("object")
-    o2 = mock("object")
-    suppress_warning {
-      def o1.__id__; 10; end
-      def o2.__id__; 10; end
-    }
-    o1.equal?(o2).should == false
-  end
-
-  it "is unaffected by overriding object_id" do
-    o1 = mock("object")
-    o1.stub!(:object_id).and_return(10)
-    o2 = mock("object")
-    o2.stub!(:object_id).and_return(10)
-    o1.equal?(o2).should == false
-  end
-
-  it "is unaffected by overriding ==" do
-    # different objects, overriding == to return true
-    o1 = mock("object")
-    o1.stub!(:==).and_return(true)
-    o2 = mock("object")
-    o1.equal?(o2).should == false
-
-    # same objects, overriding == to return false
-    o3 = mock("object")
-    o3.stub!(:==).and_return(false)
-    o3.equal?(o3).should == true
-  end
-
-  it "is unaffected by overriding eql?" do
-    # different objects, overriding eql? to return true
-    o1 = mock("object")
-    o1.stub!(:eql?).and_return(true)
-    o2 = mock("object")
-    o1.equal?(o2).should == false
-
-    # same objects, overriding eql? to return false
-    o3 = mock("object")
-    o3.stub!(:eql?).and_return(false)
-    o3.equal?(o3).should == true
+  it "is an alias of BasicObject#==" do
+    BasicObject.instance_method(:equal?).should == BasicObject.instance_method(:==)
   end
 end

core/basicobject/equal_value_spec.rb

@@ -7,4 +7,48 @@
   end
 
   it_behaves_like :object_equal, :==
+
+  it "is unaffected by overriding __id__" do
+    o1 = mock("object")
+    o2 = mock("object")
+    suppress_warning {
+      def o1.__id__; 10; end
+      def o2.__id__; 10; end
+    }
+    (o1 == o2).should == false
+  end
+
+  it "is unaffected by overriding object_id" do
+    o1 = mock("object")
+    o1.stub!(:object_id).and_return(10)
+    o2 = mock("object")
+    o2.stub!(:object_id).and_return(10)
+    (o1 == o2).should == false
+  end
+
+  it "is unaffected by overriding equal?" do
+    # different objects, overriding equal? to return true
+    o1 = mock("object")
+    o1.stub!(:equal?).and_return(true)
+    o2 = mock("object")
+    (o1 == o2).should == false
+
+    # same objects, overriding equal? to return false
+    o3 = mock("object")
+    o3.stub!(:equal?).and_return(false)
+    (o3 == o3).should == true
+  end
+
+  it "is unaffected by overriding eql?" do
+    # different objects, overriding eql? to return true
+    o1 = mock("object")
+    o1.stub!(:eql?).and_return(true)
+    o2 = mock("object")
+    (o1 == o2).should == false
+
+    # same objects, overriding eql? to return false
+    o3 = mock("object")
+    o3.stub!(:eql?).and_return(false)
+    (o3 == o3).should == true
+  end
 end

core/dir/delete_spec.rb

@@ -1,6 +1,5 @@
 require_relative '../../spec_helper'
 require_relative 'fixtures/common'
-require_relative 'shared/delete'
 
 describe "Dir.delete" do
   before :all do
@@ -11,5 +10,55 @@
     DirSpecs.delete_mock_dirs
   end
 
-  it_behaves_like :dir_delete, :delete
+  before :each do
+    DirSpecs.rmdir_dirs true
+  end
+
+  after :each do
+    DirSpecs.rmdir_dirs false
+  end
+
+  it "removes empty directories" do
+    Dir.delete(DirSpecs.mock_rmdir("empty")).should == 0
+  end
+
+  it "calls #to_path on non-String arguments" do
+    p = mock('path')
+    p.should_receive(:to_path).and_return(DirSpecs.mock_rmdir("empty"))
+    Dir.delete(p)
+  end
+
+  it "raises an Errno::ENOTEMPTY when trying to remove a nonempty directory" do
+    -> do
+      Dir.delete DirSpecs.mock_rmdir("nonempty")
+    end.should.raise(Errno::ENOTEMPTY)
+  end
+
+  it "raises an Errno::ENOENT when trying to remove a non-existing directory" do
+    -> do
+      Dir.delete DirSpecs.nonexistent
+    end.should.raise(Errno::ENOENT)
+  end
+
+  it "raises an Errno::ENOTDIR when trying to remove a non-directory" do
+    file = DirSpecs.mock_rmdir("nonempty/regular")
+    touch(file)
+    -> do
+      Dir.delete file
+    end.should.raise(Errno::ENOTDIR)
+  end
+
+  # this won't work on Windows, since chmod(0000) does not remove all permissions
+  platform_is_not :windows do
+    as_user do
+      it "raises an Errno::EACCES if lacking adequate permissions to remove the directory" do
+        parent = DirSpecs.mock_rmdir("noperm")
+        child = DirSpecs.mock_rmdir("noperm", "child")
+        File.chmod(0000, parent)
+        -> do
+          Dir.delete child
+        end.should.raise(Errno::EACCES)
+      end
+    end
+  end
 end

core/dir/rmdir_spec.rb

@@ -1,15 +1,7 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
-require_relative 'shared/delete'
 
 describe "Dir.rmdir" do
-  before :all do
-    DirSpecs.create_mock_dirs
+  it "is an alias of Dir.delete" do
+    Dir.method(:rmdir).should == Dir.method(:delete)
   end
-
-  after :all do
-    DirSpecs.delete_mock_dirs
-  end
-
-  it_behaves_like :dir_delete, :rmdir
 end

core/dir/shared/delete.rb

@@ -1,15 +1,7 @@
 require_relative '../../spec_helper'
-require_relative 'fixtures/common'
-require_relative 'shared/delete'
 
 describe "Dir.unlink" do
-  before :all do
-    DirSpecs.create_mock_dirs
+  it "is an alias of Dir.delete" do
+    Dir.method(:unlink).should == Dir.method(:delete)
   end
-
-  after :all do
-    DirSpecs.delete_mock_dirs
-  end
-
-  it_behaves_like :dir_delete, :unlink
 end

core/dir/unlink_spec.rb

@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "FalseClass#inspect" do
-  it "returns the string 'false'" do
-    false.inspect.should == "false"
+  it "is an alias of FalseClass#to_s" do
+    false.method(:inspect).should == false.method(:to_s)
   end
 end

core/false/inspect_spec.rb

@@ -1,11 +1,7 @@
 require_relative '../../spec_helper'
 
 describe "FalseClass#^" do
-  it "returns false if other is nil or false, otherwise true" do
-    (false ^ false).should == false
-    (false ^ true).should == true
-    (false ^ nil).should == false
-    (false ^ "").should == true
-    (false ^ mock('x')).should == true
+  it "is an alias of FalseClass#|" do
+    false.method(:^).should == false.method(:|)
   end
 end

core/false/xor_spec.rb

@@ -1,7 +1,7 @@
 require_relative '../../spec_helper'
-require_relative '../../shared/file/zero'
 
 describe "File.zero?" do
-  it_behaves_like :file_zero, :zero?, File
-  it_behaves_like :file_zero_missing, :zero?, File
+  it "is an alias of File.empty?" do
+    File.method(:zero?).should == File.method(:empty?)
+  end
 end

core/file/zero_spec.rb

@@ -0,0 +1,7 @@
+require_relative '../../spec_helper'
+require_relative '../../shared/file/zero'
+
+describe "FileTest.empty?" do
+  it_behaves_like :file_zero, :empty?, FileTest
+  it_behaves_like :file_zero_missing, :empty?, FileTest
+end